Device for assistance in the wound healing processes

ABSTRACT

A device that assists in the wound healing process that takes into account the different skin types that are laser-treated in order to optimise the effectiveness of the wound-healing processes and to avoid any burning. The device comprises a laser source suitable for emitting a beam whose wavelength is between approximately 800 nanometres and approximately 820 nanometres and includes a control module suitable for controlling the laser source according to data regarding the skin type of the patient to be treated.

FIELD OF THE INVENTION

The invention is related to the field of assistance in skin woundhealing, and in particular to assistance in wound healing processesusing a laser beam.

PRIOR ART

Various solutions are known in the prior art, consisting of promotingwound healing by using an external energy source. These solutionsconsist of treating the tissue with light energy emitted by a lasersource onto the tissues in order to selectively heat specific parts ofthe skin, during a very short laser firing time (less than one second).The selective nature of the treatment means temperature elevation in theirradiated tissue areas is restricted.

In European patent application EP265470, for example, a device is known,which is used for uniting the lips of a wound. It includes a laser whoseemission wavelength is chosen such that it can perform tissue bondingand unite the lips of the wound, and a holding piece suitable for beingsecured to the tissue around the wound so as to hold the lips of saidwound in contact, at least while the wound is exposed to said laserradiation.

The key idea is to unite both skin and vessels, by using sufficientlaser energy to achieve an increase in tissue temperature beyond 60° C.,suitable for denaturing and achieving interdigitation of the collagenfibres. This temperature is currently acknowledged to be the level abovewhich irreversible heat damage is caused if tissue is heated for longerthan one second, leading to tissue coagulation and necrosis throughburning, such as to slow and reduce the quality of the healing process.

Nevertheless, the solutions known the prior art invariably use identicalfiring power values, regardless of the skin type on which the treatmentis carried out. However, the effects of a laser beam on the skin varysubstantially from one skin type to another. Incorrect choices withregard to laser settings can thus lead to ineffective treatment or toburns.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to solve the aforementioned problem,by offering a device for assistance in the wound healing process thattakes into account the different skin types that are laser-treated inorder to optimise the effectiveness of the wound-healing processes andto avoid any burning.

To this end, the invention provides a device for assistance in the skinwound healing process, comprising a laser source suitable for emitting abeam whose wavelength is between approximately 800 nanometres andapproximately 820 nanometres.

The device of the invention includes a control module suitable forcontrolling the laser source according to data regarding the skin typeof the patient to be treated.

“Laser source” is here understood to refer to the device emitting thebeam that is focused on the skin to be treated. The laser sourceincludes, in particular, the laser diode(s) and the optical means usedto shape the radiation emitted therefrom.

“Control” is here understood to refer to any type of control or commandinfluencing the characteristics of the beam focused on the skin. Suchcharacteristics may for instance include the power, duration, shape orspeed of movement of the laser beam.

In a first embodiment of the invention, the control module is suitablefor controlling the laser source according to the skin phototype of thepatient to be treated.

More particularly, the control module is suitable for controlling alaser source such that it emits, for a duration of less than 20 seconds,a fluence of:

-   -   between approximately 80 J/cm² and approximately 130 J/cm² when        the skin phototype is of category I, II or III,    -   between approximately 60 J/cm² and approximately 100 J/cm² when        the skin phototype is of category IV, and    -   between approximately 20 J/cm² and approximately 60 J/cm² when        the skin phototype is of category V or VI.

In a preferred variant of the invention, the control module is suitablefor controlling a laser source such that it emits radiation for aduration that varies according to the phototype, whereby the durationwill, in particular, decrease as the phototype number (category)increases.

More particularly, the control module is suitable for controlling alaser source such that it emits:

-   -   for approximately 5 seconds to approximately 15 seconds when the        skin phototype is of category I, II III or IV, and    -   for a duration of greater than 10 seconds and less than 20        seconds when the skin phototype is of category V or VI.

In a second embodiment of the invention, the control module is suitablefor controlling the laser source according to the lightness of the skinarea to be treated. The parameter L* (for lightness) is part of theL*a*b* colour space description created by the International Commissionon Illumination. The parameter L* is a non-linear function of luminanceand does not have a measurement unit. L*=0 represents the colour blackand L*=100 represents the colour white.

More particularly, the control module is suitable for controlling alaser source such that it emits, for a duration of less than 20 seconds,a fluence of:

-   -   between approximately 110 J/cm² and approximately 130 J/cm² when        the lightness of the skin area to be treated is greater than 80,    -   between approximately 100 J/cm² and approximately 110 J/cm² when        the lightness of the skin area to be treated is between        approximately 75 and approximately 80,    -   between approximately 80 J/cm² and approximately 100 J/cm² when        the lightness of the skin area to be treated is between        approximately 70 and approximately 75,    -   between approximately 60 J/cm² and approximately 80 J/cm² when        the lightness of the skin area to be treated is between        approximately 65 and approximately 70,    -   between approximately 40 J/cm² and approximately 60 J/cm² when        the lightness of the skin area to be treated is between        approximately 55 and approximately 65,    -   between approximately 30 J/cm² and approximately 50 J/cm² when        the lightness of the skin area to be treated is between        approximately 45 and approximately 55, and    -   between approximately 20 J/cm² and approximately 30 J/cm² when        the lightness of the skin area to be treated is less than 45,

In a preferred variant, the control module is suitable for controlling alaser source such that it emits radiation for a duration that variesaccording to the lightness value of the skin area to be treated, wherebythe duration will, in particular, increase as the lightness valueincreases.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will best be understood through reading thefollowing description, given purely by way of example, referring to theappended illustrations, wherein:

FIG. 1 is a graph illustrating a logarithmic relationship betweenexposure time and temperature for inducing a heat shock response,

FIG. 2 is a graph illustrating the different phases of healing for acutaneous wound,

FIG. 3 is a graph illustrating the different absorption coefficients ofthe main chromophores, as a function of laser source wavelength,

FIG. 4 is a graph illustrating the skin penetration (percentage depth)of a laser beam as a function of wavelength,

FIG. 5 is a graph illustrating the influence of skin phototype on skintemperature elevation,

FIG. 6 is a graph illustrating the influence of skin lightness on skintemperature elevation,

FIG. 7 is a graph showing a conventional laser beam profile and a laserbeam profile as claimed in the invention,

FIG. 8 gives a schematic illustration of a laser beam conversion deviceas claimed in the invention,

FIGS. 9 and 10 are diagrams illustrating a dermatological treatmentdevice as claimed in the invention,

FIG. 11 is a simplified diagram of a safety strip as claimed in theinvention,

FIG. 12 illustrates the design that could be printed on a safety stripas claimed in the invention,

FIG. 13 is a schematic representation of the communications between anRFID component and the two microcontrollers in a device as claimed inthe invention,

FIGS. 14 a to 14 c are graphs illustrating various temperature increasescenarios on the surface of an area of treated tissue, and

FIGS. 15 and 16 are logic flowcharts showing the processes at work inthe microcontrollers in a device as claimed in the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is based on moderate heating to provide heat treatment toa limited volume of cutaneous tissue surrounding and including a presentor future cutaneous lesion (a future lesion, for instance, in the caseof surgical incisions). As stated above, the invention does not providefor the selective heating of one or more skin constituents, butdescribes heating the whole of a volume located throughout the thicknessof the skin (epidermis, dermis, upper layer of the subcutaneous tissue)in order to generate a biological response to the heat stress or thermalconditioning throughout the tissue. The choice of beam and all relatedparameters is therefore based on these specifications.

FIG. 1 illustrates a logarithmic relationship between exposure time onthe y-axis (units in seconds) and the temperature for inducing a heatshock response along the x-axis (units in degree Celsius). Heat shockresponse is a cellular mechanism used to maintain stability when a shock(e.g. heat shock) is undergone. The heat shock response often involvesthe production of heat shock proteins (HSP), a protein group that canhelp accelerate the healing process.

The invention does not aim to alter the cell structure, but to influencethe healing process by inducing HSP production. Indeed, uncontrolledhyperthermia can quickly lead to tissue damage and consequently totissue denaturing and destruction. Using thermal conditioning, theinvention provides for induction of a localised fever whose maximumtemperature is controlled to prevent tissue damage.

By directing a source of electromagnetic energy such as a laser at thewounded tissue zone, thermal conditioning is induced such as to alterthe inflammatory process. The link between a controlled temperatureincrease (moderate hyperthermia), HSP production and the inflammationprocess has been established in the prior art.

Referring to FIG. 2, the healing process involves three phases followingthe initial thrombosis:

-   -   inflammation (21),    -   proliferation (22) and,    -   remodelling (23).

The x-axis of this graph shows the time since start of healing and they-axis shows a level of response to a given heat shock and hence a levelof HSP production.

A laser beam skin wound treatment process consists of directing lightenergy onto the tissue with the aim of generating moderate andcontrolled hyperthermia as early as possible in the healing process inorder to prevent scarring and accelerate tissue regeneration, ratherthan correcting this scarring once the scar itself has appeared. Thetime at which the wound is treated must therefore be selected carefullywith respect to the inflammation phase.

An optimum treatment window should be defined, to ensure that the peakof HSP production coincides with the inflammation phase. Since the HSPproduction peak may occur up to 24 hours after heat stress has beenundergone, the conditioning treatment may take place up to 24 hoursbefore the lesion appears.

Beam Selection:

The choice of beam and all related parameters is based on precisespecifications. A digital simulation model was used, based on the finiteelement method, taking into account interactions between the light andthe main chromophores in the treatment region, in order to confirm thetheoretical choices.

Wavelength Selection:

FIG. 3 is a graph with three curves showing the energy absorptioncoefficient (y-axis) as a function of the energy wavelength (x-axis) forthe following skin constituents: melanin, shown as curve 301,haemoglobin, shown as curve 302, and water, shown as curve 303.

FIG. 4 is a graph showing the rate of absorption of each skin layer forvarious wavelengths.

Referring to these figures, it can be observed that light absorption bythe various chromophores can vary considerably according to wavelength.

Since the melanocytes are located in the basal layer of the epidermis,the wavelength must be greater than 800 nm in order to pass through thislayer without being fully absorbed. At wavelengths of less than 590 nm,haemoglobin is the predominant chromophore and is therefore highlyabsorbent. However, at red and near-infrared wavelengths (between 600 nmand 1000 nm), there is relatively little absorption since neither waternor blood absorb energy at these wavelengths. Finally, for wavelengthsgreater than 1800 nm, absorption in water is extremely high and thisabsorption becomes the predominant factor.

The range of wavelengths to be used must therefore be between 800 nm and1800 nm. In a preferred embodiment, the wavelength will be 810 nm or 910nm. Advantageously, wavelengths of 1200 nm would minimise the absorptionby melanin, but current technology does not provide a sufficientlypowerful beam from laser diode source at this wavelength.

Laser Fluence Selection

FIGS. 5 and 6 illustrate the influence of skin type on the temperaturereached by said skin under laser illumination at a wavelength of 810nanometres.

FIG. 5 shows skin temperature curves as a function of laser fluence injoules per cm² for patient with different skin phototypes. The fluenceof the beam is the energy transmitted per cm².

These curves were obtained in experiments involving patients withdifferent skin phototypes, whereby curve C1 describes skin of phototypeV, curve C2 describes skin of phototype IV, curves C3, C4 and C6 alldescribe skins of phototype III and curve C5 describes skin of phototypeII.

Phototype is a numerical classification of skin type that is well knownin the field of dermatology. It takes into account a person's geneticdisposition, reaction to sun exposure and tanning habits. Skinphototype, as determined by the score given in the Fitzpatrick skintyping test, is commonly used by healthcare professionals and can helpsupport various diagnostic and treatment procedures for the skin.

As can be seen from FIG. 5, skin heating depends heavily on skinphototype. Moreover, a spread of behaviours is observable even within asingle phototype category, as illustrated by curves C3, C4 and C6.

The inventors thus observed that, for a wavelength of between 800nanometres and 820 nanometres, the following ranges of fluence valuesprovide for an effective process of wound healing, as sought, whilstavoiding any burning due to overexposure:

-   -   fluence between approximately 80 J/cm² and approximately 130        J/cm² when the skin phototype is of category I, II or III,    -   fluence between approximately 60 J/cm² and approximately 100        J/cm² when the skin phototype is of category IV, and    -   fluence between approximately 20 J/cm² and approximately 60        J/cm² when the skin phototype is of category IV.

Outside of this range of fluence values, a reduced healing effect orburning may be observed, or wholly ineffective treatment.

In addition, the fluence should be transmitted for a duration that isless than a specified threshold, in order to promote effective skinheating, leading to the desired healing effect. A maximum fluencetransmission time of less than 20 seconds is suitable for achieving thedesired heating effect. Beyond this duration, the heating is tooshallow. The exposure time can, for example, be managed by controllingthe duration of the laser pulses.

The spread of temperature values observed in a group of people with thesame phototype may have various causes. The Fitzpatrick skin typing testdoes not only take into account skin colour, but also considers criteriasuch as eye and hair colour, skin reaction to sunlight or tanninghabits. Although phototype values given by the Fitzpatrick test are agood indicator, enabling the fluence of the laser treatment to beadjusted without requiring any specific equipment for detecting skintype, the precision of the phototype scale remains somewhat limited.

FIG. 6 shows skin temperature curves as a function of laser fluence injoules per cm2 for skins with different lightness values, as measuredwith a conventional chromameter.

As can be seen from curves C7, C8 and C9, obtained from experiments onskin with the same phototype but with lightness values of 70, 73 and 77respectively, temperature elevation is heavily dependent of thelightness of said skin.

The inventors thus observed that, for a wavelength of between 800nanometres and 820 nanometres, the following ranges of fluence valuesprovide for an effective process of wound healing, as sought, whilstavoiding any burning due to overexposure:

-   -   fluence between approximately 110 J/cm² and approximately 130        J/cm² when the lightness of the skin area to be treated is        greater than 80,    -   fluence between approximately 100 J/cm² and approximately 110        J/cm² when the lightness of the skin area to be treated is        between approximately 75 and approximately 80,    -   fluence between approximately 80 J/cm² and approximately 100        J/cm² when the lightness of the skin area to be treated is        between approximately 70 and approximately 75,    -   fluence between approximately 60 J/cm² and approximately 80        J/cm² when the lightness of the skin area to be treated is        between approximately 65 and approximately 70,    -   between approximately 40 J/cm² and approximately 60 J/cm² when        the lightness of the skin area to be treated is between        approximately 55 and approximately 65,    -   between approximately 30 J/cm² and approximately 50 J/cm² when        the lightness of the skin area to be treated is between        approximately 45 and approximately 55, and    -   between approximately 20 J/cm² and approximately 30 J/cm² when        the lightness of the skin area to be treated is less than 45.

Analogously to what has described above, said fluence should betransmitted for a duration of less than 20 seconds in order to producethe desired healing effect.

Moreover, the inventors also noted that the darker the skin is, thelonger the duration of fluence transmission that should be applied.Indeed, with dark skins, the transmission of light energy over a shortduration has the effect of heating surface layers of the skin ratherthan heating in depth. If the illumination is spread over time, the skinis heated by thermal diffusion.

Notably, the laser beam is controlled such that its duration variesaccording to the phototype, whereby the duration will in particulardecrease as the phototype number (category) increases. Moreparticularly, once the fluence has been determined according to skinphototype, it is preferable to have illumination for approximately 5seconds to approximately 15 seconds when the skin phototype is ofcategory I, II, III or IV and illumination for a duration of greaterthan 10 seconds and less than 20 seconds when the skin phototype is ofcategory V or VI.

Analogously, the laser beam is controlled such that it varies accordingto the lightness value of the skin area to be treated, whereby theduration will in particular increase as lightness increases.

Spot Shape Selection:

The shape of the laser spot must also be studied in order to providedeep heating and stimulate all tissues involved in the skin woundhealing process: the subcutaneous tissue, dermis, and epidermis. Sincedepth is near-proportional to the laser spot diameter, a diametergreater than or equal to 3 mm will be preferred in the case of a roundspot. Ideally, the spot shape could also be tailored to the geometry ofthe area to be treated, to enable the most homogeneous distributionpossible of light energy within the target tissue. In a preferredembodiment, a rectangular spot shape whose width is at least 3 mm andwhose length may be several centimetres will be selected, in order totreat linear wounds.

Temperature Precision in the Heated Volume and Laser Beam Profile:

The invention additionally relates to the temperature precision achievedwithin the heated volume. The digital model developed can be used tooptimise all parameters and achieve a minimum temperature of 45° C.(temperature required to induce heat stress) and a maximum temperatureof 55° C. As described in the prior art, temperatures in excess of 60°C. can induce protein denaturing and therefore counteract the desiredeffect. The maximum temperature of 55° C. means that this thresholdvalue will not be exceeded.

For these reasons, and as shown in FIG. 7, which illustrates both aconventional Gaussian beam profile (curve 512) and the beam profile of adevice as claimed in a possible embodiment of the invention (curve 510),a conventional Gaussian beam profile is not the most suitable profile.Indeed, as the name suggests, the energy distribution is similar to aGaussian function, which has the direct effect of heating the skinsurface in a non-uniform manner, with a major temperature peak in thecentre of the irradiated zone. The temperature gradient will thereforebe too great with respect to the temperature range in which it isdesirable to operate.

A flat-top (or top-hat) profile (510) is consequently to be preferred toa Gaussian profile in order to ensure the skin surface temperature ishomogenised, as is the temperature of the heated volume. This flat-toppower profile, shown as curve 510, gives a more homogeneous heatingeffect throughout the heated area, rather than a selective heatingaction. This profile is defined by three components:

-   -   the ratio of wavefront width (515) to full-width half-maximum        (FWHM) (514),    -   the rate of variation (516) along the wavefront width (515),    -   the nominal power (518) which is the mean power along the        wavefront width (515).

One feature of a flat-top profile is a minimal rate of variation (516)along the wavefront width, with a maximal wavefront width-to-FWHM ratio.Advantageously, a flat-top profile will have a rate of variation of lessthan 5% and a ratio of wavefront width-to-FWHM of greater than 90%.

The spot shape will depend on the medical indication. In a preferredembodiment and in a configuration chosen for treating incisions, thespot dimensions will be 20 mm by 4 mm, and the rate of variation lessthan +/−20% of nominal power (518).

In order to achieve this particular profile, the invention provides ameans for shaping the laser beam emitted by the diode (since on outputfrom the diode the laser beam has a Gaussian profile). An example ofsuch a system is shown in FIG. 8.

In one possible embodiment of the invention therefore, the laser beamshaping means (61) is positioned downstream of a laser diode (62),advantageously characterised in that its emission width is 200 μm by 5μm and its divergence is 8×35°. An optical fibre (63) positioned infront of the diode acts as a cylindrical lens to reduce divergence ofthe diode's fast axis advantageously to approximately 5°. The laser beamthen passes through the laser beam shaping means (61), which includes asystem of two lens arrays (64) and a cylindrical lens (66), which splitsthe original beam into as many beams as there are lenses in the lensarray (64). Each sub-beam is focused at the desired distance and allthese beams are then superimposed to achieve a flat-top profile.

The beam's focal distance depends chiefly on the focal length of thecylindrical lens. The homogeneous nature of the profile depends howeverboth on the focal length of the cylindrical lens and on the focal lengthof the two lens arrays. Furthermore, to achieve the most homogeneousflat-top beam profile possible, the input beam must strike as manylenses in the array as possible (the greater the number of sub-beamsformed, the more likely the sub-beams are to tend towards a flat-topprofile when combined). There is, therefore, a balance to be struckbetween the distance between the diode and the first lens array and theangle of divergence, in order to maximise homogeneity of the flat-topprofile, whilst reducing the length of the final system.

PREFERRED EMBODIMENTS

In order for the technique to be accessible to as many users aspossible, the device is designed to be easy and safe to use under allcircumstances and in all locations in which it may be used, from ageneral practitioner's surgery to the sterile environment of anoperating theatre. Since users may travel or make regular visits, thesize and portability of the device is also a key factor. In addition, asdescribed above, the invention provides that the light source is appliedas early as possible in the healing process in order to prevent theappearance of scarring, rather than correcting this once the scar hasappeared. For this purpose, users need a medical device that can enableearly intervention, i.e. directly in the operating theatre in a sterileenvironment.

The medical device should therefore be designed to be small, portable,easy to use with one hand and autonomous (wireless) and further designedto avoid jeopardising the cleanliness or sterility of the environment inwhich it is used.

One embodiment of a device as claimed in the invention will now bedescribed, referring to FIGS. 9 and 10.

A dermatological treatment device (70) as claimed in the inventionincludes a closed optical unit (722), including at least one lasersystem (72) comprising a power laser diode whose wavelength is between800 nm and 820 nm, preferably equal to 810 nanometres and whose power isgreater than 1 W and less than 25 W, and conversion means (74)consisting of a lens array or a phase array. The laser system (72) andconversion means (74) are designed to emit a laser beam with theaforementioned advantageous characteristics. Optical unit (722) may alsoinclude a sighting laser (73), whose power is less than 1 mW forinstance, in order for said sighting laser to provide comfort in use andnot generate any biological response. In order to ensure this sightinglaser (73) is visible, its wavelength may for instance be between 480 nmand 650 nm (red colour).

The invention provides that optical unit (722) is removable andinterchangeable in order to facilitate maintenance of treatment device(70) and ensure its flexibility (ability to change diode type accordingto the desired treatment type). The invention therefore provides thedevice user (e.g. medical practitioner) with a selection of opticalunits, each of which will have different configurations and all of whichcomply with the safety-related constraints (the user cannot change thesettings himself).

Treatment device (70) also comprises an energy source (battery) (71) forfull autonomy. This battery may be interchangeable.

Treatment device (70) includes one or more electronic circuits (710)whose function is to manage power supply to the device and the variouscomponents in the device.

The treatment device includes an RFID reader (711) (e.g. RFID antenna),used to make the device safe by ensuring that the laser only fires whenit is in the vicinity of an RFID component (tag) affixed close to thetreatment area, thus preventing any risk of harm for the user, patientand other nearby persons. This system also enhances treatment safety byreading pre-recorded settings from the tag, meaning that thepractitioner cannot accidentally change any potentially dangerousparameter (chiefly laser power and firing time). The laser settings arecontrolled on the basis of information transmitted by the RFIDcomponent, which contains configuration data that can adjust the firingpower, firing time and number of pulses, according to the user'schoices, in order to obtain the fluence values described above accordingto the skin phototype of the patient to be treated.

The user will select the attachment element according to the nature ofthe treatment to be performed, and the selected tag will transmit asignal or information which will control the laser emissions. Theattachment element consists for instance of a patch formed by a piece ofadhesive fabric that includes a radio frequency identification (RFID)tag, consisting of an antenna design that enables inductive coupling forpower supply to a high frequency component and transmission of a highfrequency signal emitted by said component.

The attachment element must be placed close to the treatment zone suchthat treatment device (70) is within interaction range of the tagthroughout the duration of treatment.

These RFID components are widely described in the prior art. However,the invention provides that the RFID component also plays a role inautomating the process. The RFID component has an identifier whichrefers to a settings table in the laser software. This table containspreset values for firing power and firing time and also the type ofpatient to be treated (for a safety check by the practitioner). Whenusing the device, the user simply selects a safety strip (containingRFID components) based on the patient's skin phototype and indication(wound, acne treatment, skin remodelling etc.). Unlike other lasersystems on the market, the user cannot adjust the operating settings.Treatment parameters are therefore based solely on the choice of stripcontaining the treatment identifier.

Advantageously, the distance between the RFID component and thetreatment device (70) is between one and fifteen centimetres. Thisdistance is assessed by the limited range of the interaction meansbetween said component and treatment device (70) or by a range-finder,for instance an ultrasound range-finder integrated in the device.

The treatment device also includes a pyrometer (712), used to monitorthe temperature increase that can cause superficial burning (temperaturegreater than 60° C.). The pyrometer (712) is used to set up a closedloop on the laser beam. Pyrometer (712) is in fact a safety componentthat monitors skin surface temperature. It operates to “lock down” ordeactivate laser firing if the temperature reaches a preset thresholdvalue. Pyrometer (712) can also be used in a more advanced way within aclosed control loop in order to readjust the laser settings.

In general, the temperature at the surface and deeper in the epidermiswill depend on a variety of parameters such as:

1—wavelength, which is a key factor in the absorption and scattering oflight by the various chromophores (water, haemoglobin, melanin),2—laser power, causing heating to a greater or lesser depth,3—spot shape and size, which influence the heat distribution at depth,4—beam profile, which has a direct impact on the temperature gradientacross a beam cross-section (Gaussian profile, flat-top profile),5—firing time which, at a given power, the longer it is promotes athermal diffusion heating system,6—finally, parameters directly related to the patient, the mostsignificant of which is likely to be the skin phototype.

There may not therefore be a general correlation between the surfacetemperature of the epidermis and the temperature of lower layers.However, if all laser-related parameters (points 1 to 5) are fixed, itis possible to “predict” the temperature increase in the tissue on thebasis of a human factor, for instance the phototype.

In addition, a transparent optical window (713) in the wavelength rangebetween 480 nm and 1.4 μm shall be provided. In a preferred embodiment,potassium bromide that is transparent from wavelengths from 450 nm to 10μm could be chosen.

A standby system could be also added to the device, to operate when thedevice is not used for a preset length of time. Standby mode isinterrupted as soon as user presses either of the fire buttons. Thistype of system saves battery power, on the one hand, but in particularprevents the sighting laser (even a low power laser) from causing eyedamage.

In addition, the treatment device could include a cooling systemcomprising an internal radiator (714) connected directly or via a heatpipe to the laser diode. Furthermore, one possible embodiment of theinvention provides a natural and/or forced ventilation device to extractheat generated by the laser diode from the device in a sterile manner inorder to avoid jeopardising the sterility of the operating area in whichthe treatment device (70) is used.

Advantageously, the device could be fitted with a user interface toprovide the user with information on the operating parameters(wavelength, settings contained in the RFID component and read by theRFID treatment device, temperature measured by the pyrometer).

Details of the user interface on a treatment device as claimed in theinvention will now be given. Advantageously, the user interface on atreatment device of the invention includes the following items:

-   -   an LCD screen (75), feeding back information to the user on the        operating settings and parameters of the device of the invention        (the LCD screen may be a touch-screen),    -   an emergency stop button (76), which the user can activate to        quickly shut down (20) the device in a emergency,    -   an on/off button (77) to switch the device on or off,    -   a double button system (88) to safely fire the laser. The double        button system (two buttons, one on either side) makes the firing        operation safe in that the laser can only fire when both buttons        are held down by the user. As soon as the user releases either        button, the laser immediately stops firing. Consequently, if the        handpiece were to be inopportunely placed on a work surface and        one of the buttons was resting on an item on the work surface,        the laser could not fire.    -   an indicator light (89) to show the user that the device is        operating,    -   a buzzer (717) to warn the user of a problem (battery problem,        high temperature measured by the pyrometer).

Advantageously, a possible embodiment of the invention provides aremovable sterile sleeve (80) designed to contain the device and isolateit from the external environment. This sleeve can be understood as asterile casing in which the device is placed in order to ensure that thearea in which the device is used remains sterile. Advantageously,removable sleeve (80) is designed not to interfere with the laser beam.For this purpose the device shall have a window that is transparent tothe predefined wavelengths, in order to allow a beam whose wavelength iswithin the range of preset wavelengths to pass through. Removable sleeve(80) is further designed not to interfere with pyrometer (712) or RFIDreader (711) operation. Removable sleeve (80) also allows heatextraction without causing a detrimental effect on the sterileenvironment in which treatment device (70) is used. Using this sleeve,the laser can be fired without altering the sterility of the sleeve'soutside surfaces.

The sleeve must obviously be sealed and have a sealed closure system, inorder to provide a microbial barrier between the device and its externalsurroundings. Nevertheless, this sterile barrier must not hinder theextraction of heat generated by the device. The sleeve thereforecontains at least two filters (an air inlet and air outlet filter) toallow air circulation inside the sleeve.

Moreover, the sleeve must not hinder access to the device controls(firing buttons, switch, emergency stop button), prevent informationfrom being read (LCD screen, indicator lights) or the device from beinggripped. In a preferred embodiment, the sleeve shall therefore comprisea rigid section at the bottom of the device for correct positioning anda flexible transparent upper section covering the rest of the device.

Since surfaces (81) and (82) are in contact with the patient, the riskthat the sleeve could come into contact with blood, particularly whentreating an incision, should not be ignored. Indeed, if the sleeve is incontact with blood, the blood can accumulate on it as the sleeve ismoved across the rest of the incision. Since the laser beam passesthrough the sleeve, it could be absorbed by these traces andconsequently lose part of the treatment energy in this zone. In apreferred embodiment, treatment device (70) and the lower rigid part(87) of sleeve (80) in contact with the treatment area both include arecess (83) opposite the laser beam output, ensuring there is no directcontact with the patient and therefore no fouling or contamination. Thisdesign also ensures a distance between the beam shaping system outputand the tissue zone to be treated.

The sleeve therefore comprises one rigid section and one flexiblesection (to be handheld and for easy use of the buttons). It is intendedthat both sections be made of PVC, with a thickness of between 2 and 3tenths of a millimetre for the flexible section and a few millimetresfor the rigid section.

RFID Component

Referring to FIG. 11, and as described above, the treatment shall bemade safe and controlled by means of a safety strip (90) containing anRFID chip which will transmit the various operating settings to thelaser device, on the basis of the medical indication and skin phototypeof the patient to be treated. Said safety strip (90), which may beproduced in several different lengths (e.g. 4, 10 and 20 cm), is affixedapproximately 5 mm away from the zone to be treated.

The safety strip comprises two adhesive attachment elements: onedouble-sided adhesive element (91) and another single-sided adhesiveelement (93). These two elements sandwich the RFID components (92),which are arranged every 2 cm. The safety strip may, for instance, be 2cm wide.

Lower adhesive element (91) is in contact with the patient's skin. Itmust therefore be biocompatible and offer appropriate adhesion to theskin during use. Lower adhesive element (91) must stick to the patient'sskin and also bond correctly with both the RFID component and upperadhesive element (93). The lower adhesive element is therefore adouble-sided adhesive.

The safety strip manufacturing process shall include a sterilisationstage.

Upper adhesive sub-element (93) must be a single-sided adhesive in orderto be assembled with RFID component (92) and lower adhesive element(91). As shown in FIG. 12, information shall be printed on upper section(93), such as skin phototype, the company name, product number and ascale to help the practitioner gauge progress of the treatment.

Upper adhesive element (93) is designed not to interfere with RFIDcommunication between the RFID reader (711) (see FIG. 9) in the deviceand the (25) RIFD components (92). The RFID components (92) must complywith the ISO 15693-3 standard. The mandatory and optional sections, asdefined by said standard, are to be implemented. Since the RFIDtransmission range is critical, RFID components (92) as claimed in theinvention shall be such that this value can be fixed once the “RFIDcomponent-RFID reader” pair has been selected. The size of said RFIDcomponents may for instance be 14 mm×14 mm and the thickness less than 1mm. The EEPROM storage capacity of the RFID component shall be at least1024 bytes. The production process shall also include sterilisation withethylene oxide.

Communication Process Between the RFID Component and the Device

As shown in FIG. 13, the device comprises two microcontrollers (111 and112). One microcontroller (111) manages the laser, energy, thermalcontrol and the user interface. The other microcontroller (112) managesthe safety strips (90). Responsibility for managing the laser firing isshared by both microcontrollers (111 and 112). The laser may be stoppeddue to excessive temperature (15) (managed by microcontroller 111) or anemergency stop request (microcontroller 111). If the stoppage conditionsstill apply, laser treatment cannot resume.

Referring to FIGS. 14 a, 14 b and 14 c, a pyrometer (712) (see FIG. 7)stops the laser if the skin temperature exceeds a critical temperature,for instance 60° C. (managed by microcontroller 111). These figures aregraphs which show temperature curves 120, 121 and 122 (temperature indegree Celsius on the Y-axis) as a function of heating time (TC, on theX-axis). TC1, TC2 and TC3 represent the times at which the laser isstopped. If the laser has been stopped (25) by the pyrometer (712), itcan be authorised to operated once more only, after a safety delay (e.g.5 seconds), if during the first laser emission, the firing time was lessthan or equal to half the preset firing time (as managed bymicrocontroller 112). This is the case in FIG. 14 c. The figurestherefore illustrate the following scenarios:

-   -   FIG. 14 a illustrates a scenario in which the laser is stopped        (TC1) after 50% of the preset firing time has elapsed; in this        case the laser treatment cannot be resumed,    -   FIG. 14 b illustrates a scenario in which the laser is not        stopped before the end of the preset firing time (TC2),    -   FIG. 14 c illustrates a scenario in which the laser is stopped        (TC3) before 50% of the preset firing time has elapsed; in this        case the laser treatment may be resumed.

If the pyrometer (712) trips after 50% or more of the normal firing timehas elapsed (FIG. 14 a), the end of normal firing should be indicatedwith a beep (microcontroller 111). If the pyrometer (712) trips before50% of the time has elapsed, a display on the user interface shallindicate to the user that the laser treatment may be resumed.

If the user stops the laser voluntarily or otherwise and the elapsedtime is less than or equal to 75% of the preset firing time, the lasertreatment may be allowed to resume once only, after a 5 second delay.This re-authorisation is valid for a 60 minute period.

If the emergency stop system is activated (FIG. 9, button 76), achecking procedure could be provided.

The presence of an RFID component (92) is indicated by the TTL pin (113)on the microcontroller (112). The presence of an RFID component (92)gives no information regarding its status. To find out the status ofRFID component (92), a “read settings” message must be sent tomicrocontroller (112). This command requests information on thetreatment status of RFID component (92), which is in range of RFIDreader (711). The status of an RFID component (92) may be one of thefollowing:

-   -   Treated,    -   OK (Not Treated),    -   Immediate resume (identical to not treated),    -   Wait then resume (5 seconds),

Microcontroller (111) recognises five messages from microcontroller(112):

-   -   INIT: Initialising clock and device identification,    -   PARAM: Retrieve information on RFID component (92) status,        firing power and firing time (firing only allowed if status is        OK),    -   START: Start firing,    -   STOP: Stop firing,    -   PAUSE: Prematurely stop firing.

When the device starts, microcontroller (111) initialises the clock inmicrocontroller (112) with the INIT message. Both clocks aresynchronised. At the rising edge of the TTL pin (113) on microcontroller(112), microcontroller (111) requests the laser settings via the PARAMmessage. Depending on the reply message from microcontroller (112), theuser interface is updated and firing is authorised. During laseremission, microcontroller (111) indicates progress to microcontroller(112) with the messages START, STOP and PAUSE. Microcontroller (112)updates the information in the RFID components (92) according to thesemessages. The device clock is managed by microcontroller (111). It doesnot contain the exact date and time, but dating information related tothe device start-up. It operates as a timer. The device clock may bereinitialised following extended battery power loss. In this case, if anRFID component (92) has been treated, its treatment start date is laterthan the current date. Even if treatment has not been completed, RFIDcomponent (92) is considered as treated.

FIG. 15 illustrates a logic flowchart for microcontroller (111). Thusbox (1301) shows detection of the presence or otherwise of an RIFDcomponent. If not detected, the user interface will indicate that noRFID component was found (box 1302). If an RFID component is detected,the “read settings” command is initiated (box 1303) to diagnose RFIDcomponent status (box 1304). If status is OK, the device indicates viathe user interface that it is “ready” (box 1305), and if the trigger isactivated (box 1306), then microcontroller (111) sends microcontroller(112) the START message (box 1307) to indicate that laser emissionshould be started. The laser is switched on (box 1308). If the messageis WAIT, the device will indicate that it is on “standby” (box 1309) andthe process goes back to the start of the flowchart. If the message isTRT OK (treated), the device indicates that the zone has been treated(box 1310) and the process goes back to the start of the flowchart.

If firing is initiated (box A), temperature measurement (box 1311) isperformed. If the temperature is greater than 60° C., a time measurement(box 1312) is also performed. If this time value is less than 50% of thepreset firing time, a PAUSE message (box 1313) is sent tomicrocontroller (112) and the laser is switched off (box 1314).

If the temperature measured (box 1311) is less than 60° C., a timemeasurement (box 1315) is also performed. If this time value is lessthan 75% of the preset firing time, a further temperature measurement(box 1311) is performed. If, on the other hand, the time value isgreater than 75% of the preset firing time TC, a STOP message (box 1316)is sent to microcontroller (112). A temperature measurement is thenperformed (box 1317), and if temperature is less than 60° C., the firingtime is checked (box 1318). If the actual firing time is less than thepreset firing time TC (meaning that the laser treatment has not yetfinished), a further temperature check is performed (back to box 1317).This loop continues until the temperature exceeds 60° C. or until thefiring time reaches or exceeds TC. In either case, the laser is turnedoff (box 1320), and a beep (box 1321) (or any other user interfacesignal) is sent to advise user that treatment has finished in this zone,and an end of treatment message is displayed (box 1322). Coming back tobox 1312, if the actual firing time is greater than 50% of TC, a STOPmessage is sent to the microcontroller (box 1319) and the laser isturned off (box 1320). If the actual firing time is less than or equalto 50% of TC, a PAUSE message is sent to microcontroller (box 1314) andthe laser is turned off.

Referring to FIG. 15, a firing authorisation management logic flowchartfor microcontroller (112) will now be described. If an RFID tag isdetected (box 1401), microcontroller (111) waits for a message (box1402). When a message (box 1403) is received, said message is analysed.If the message is START, and the laser was last fired less than 5seconds ago (box 1405), microcontroller (111) sends the WAIT message(box 1406). If, on the other hand, the laser was last fired more than 5seconds ago, the totaLstart variable (indicating the number of times thelaser has fired) is increased by one increment (box 1407) and thelast_start variable (indicating the date at which the laser last fired)is updated (box 1408). Finally an OK message is sent (box 1409).

If the message received is STOP, the totaLstart variable is set to apredetermined maximum (box 1410) and the OK message is sent (box 1411).

If the message received is PAUSE, the end of firing date is recorded(box 1413).

Finally, if the message received is PARAM, the totaLstart variable (box1414) is analysed. If this variable is lower than the specified maximum,the TREATED message is sent (box 1415). If not, the last_start variable(box 1416) is analysed. If this variable is greater than 60 minutes, theTREATED message is sent (box 1415). If not, a check is performed to seewhether the laser was last fired more than 5 seconds ago (box 1417). Ifnot, the WAIT message is sent (box 1418). If, on the other hand, thelaser was last fired more than 5 seconds ago, the OK message is sent andthe settings are read (box 1419). The information in the RFID componentcould be selected from the following possibilities: unique RFIDcomponent identifier, manufacturing date, expiry date, device settingsidentifier based on skin type, safety strip manufacturing batch number.

Obviously, all the numerical values in this description (e.g.percentages, temperature etc.) are given simply for reference in orderto guide production of the invention. Other values could be used forinstance as determined by experimentation, whilst still remaining withinthe scope of the invention.

In a possible embodiment of the invention, the adhesive attachmentelement shall have a threefold safety role:

-   -   making the device safe by immediately stopping the device from        operating when the RFID component (92) in the adhesive        attachment element (90) is no longer within range of the RFID        reader (711) in the device.    -   defining the treatment settings. The user selects the adhesive        attachment element according to the patient's skin type, and the        pre-programmed RFID components (92) within adhesive attachment        element (90) directly transmit the appropriate information to        the device.    -   protecting integrity (single use). When in use, the device        records information about treatment status on the RFID        components (92) in the adhesive attachment element. Treatment        status may be as follows: zone not treated, zone being treated,        and zone treated. Once treatment is completed, the device, upon        receiving information about the status of the zone to be        treated, has means of preventing reuse of any adhesive        attachment element (90) whose identification means has already        been used once for treating a treatment zone. This RFID        component locking principle ensures that each adhesive        attachment element can be used only once. The direct benefit of        this system is that it prevents:        -   a repeated treatment in the same place (overdose risk            prevention)        -   reuse of a used adhesive attachment element (which was            sterile when delivered)

The means of preventing reuse of adhesive attachment element (90) coulddirectly be included in the RFID component itself.

A preferred embodiment has been described in which microcontrollers 111and 112 control the laser power and firing time on the basis of datacontained in the RFID tags in a strip chosen by the practitionerfollowing a Fitzpatrick skin typing test to ascertain the patient'sphototype. The laser control settings can be used to ensure the fluencevalues are within a range determined by the skin phototype, as describedabove, in order to achieve a suitable wound healing effect, whilstavoiding any burning, in a safe environment, secured by the use of suchstrips.

In a variant, the laser has a chromameter connected to microcontroller(111). In this case, skin lightness is used as the basis for selectingthe laser power and firing time, in order to ensure the fluence valuesare within a range determined by the lightness value, as describedabove.

1. Device for assistance in the skin wound healing process, comprising alaser source suitable for emitting a beam whose wavelength is betweenapproximately 800 nanometres and approximately 820 nanometres, whereinit includes a control module suitable for controlling the laser sourceaccording to data regarding the skin type of the patient to be treated.2. Device for assistance in the skin wound healing process, as claimedin claim 1, wherein the control module is suitable for controlling thelaser source according to the skin phototype of the patient to betreated.
 3. Device for assistance in the skin wound healing process, asclaimed in claim 2, wherein the control module is suitable forcontrolling the laser source such that it emits, for a duration of lessthan 20 seconds, a fluence of between approximately 80 J/cm² andapproximately 130 J/cm² when the skin phototype is of category I, II orIII.
 4. Device for assistance in the skin wound healing process, asclaimed in claim 2, wherein the control module is suitable forcontrolling the laser source such that it emits, for a duration of lessthan 20 seconds, a fluence of between approximately 60 J/cm² andapproximately 100 J/cm² when the skin phototype is of category IV. 5.Device for assistance in the skin wound healing process, as claimed inclaim 2, wherein the control module is suitable for controlling thelaser source such that it emits, for a duration of less than 20 seconds,a fluence of between approximately 20 J/cm² and approximately 60 J/cm²when the skin phototype is of category V or VI.
 6. Device for assistancein the skin wound healing process, as claimed in claim 2, wherein thecontrol module is suitable for controlling the laser source such that itemits radiation for a duration that varies according to the phototype,whereby the duration will, in particular, decrease as the phototypenumber (category) increases.
 7. Device for assistance in the skin woundhealing process, as claimed in claim 6, wherein the control module issuitable for controlling the laser source such that it emits forapproximately 5 seconds to approximately 15 seconds when the skinphototype is of category I, II, III or IV.
 8. Device for assistance inthe skin wound healing process, as claimed in claim 6, wherein thecontrol module is suitable for controlling the laser source such that itemits for a duration of greater than 10 seconds and less than 20 secondswhen the skin phototype is of category V or VI.
 9. Device as claimed inclaim 1, wherein the control module is suitable for controlling thelaser source according to the lightness of the skin area to be treated.10. Device for assistance in the skin wound healing process, as claimedin claim 9, wherein the control module is suitable for controlling thelaser source such that it emits, for a duration of less than 20 seconds,a fluence of between approximately 110 J/cm² and approximately 130 J/cm²when the lightness of the skin area to be treated is greater than 80.11. Device for assistance in the skin wound healing process, as claimedin claim 9, wherein the control module is suitable for controlling thelaser source such that it emits, for a duration of less than 20 seconds,a fluence of between approximately 100 J/cm² and approximately 110 J/cm²when the lightness of the skin area to be treated is betweenapproximately 75 and approximately
 80. 12. Device for assistance in theskin wound healing process, as claimed in claim 9, wherein the controlmodule is suitable for controlling the laser source such that it emits,for a duration of less than 20 seconds, a fluence of betweenapproximately 80 J/cm² and approximately 100 J/cm² when the lightness ofthe skin area to be treated is between approximately 70 andapproximately
 75. 13. Device for assistance in the skin wound healingprocess, as claimed in claim 9, wherein the control module is suitablefor controlling the laser source such that it emits, for a duration ofless than 20 seconds, a fluence of between approximately 60 J/cm² andapproximately 80 J/cm² when the lightness of the skin area to be treatedis between approximately 65 and approximately
 70. 14. Device forassistance in the skin wound healing process, as claimed in claim 9,wherein the control module is suitable for controlling the laser sourcesuch that it emits, for a duration of less than 20 seconds, a fluence ofbetween approximately 40 J/cm² and approximately 60 J/cm² when thelightness of the skin area to be treated is between approximately 55 andapproximately
 65. 15. Device for assistance in the skin wound healingprocess, as claimed in claim 9, wherein the control module is suitablefor controlling the laser source such that it emits, for a duration ofless than 20 seconds, a fluence of between approximately 30 J/cm² andapproximately 50 J/cm² when the lightness of the skin area to be treatedis between approximately 45 and approximately
 55. 16. Device forassistance in the skin wound healing process, as claimed in claim 9,wherein the control module is suitable for controlling the laser sourcesuch that it emits, for a duration of less than 20 seconds, a fluence ofbetween approximately 20 J/cm² and approximately 30 J/cm² when thelightness of the skin area to be treated is less than
 45. 17. Device forassistance in the skin wound healing process, as claimed in claim 9,wherein the control module is suitable for controlling the laser sourcesuch that it emits radiation for a duration that varies according to thelightness of the skin area to be treated, whereby the duration will, inparticular, increase as the lightness increases.